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POGeneric Repository - MVC 4 with Linq to Entities
 

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  1. POGeneric Repository - MVC 4 with Linq to Entities
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    <p>I think there is something very simple that I am missing or clearly not understanding. I am attempting to create a MVC 4 project that utilizes EF with a model generated by a database. I am attempting to follow the UnitOfWork/Repository design pattern.</p> <p>I have the following interface for a generic repository:</p> <pre><code>public interface IRepository&lt;T&gt; { IEnumerable&lt;T&gt; GetAll(); IEnumerable&lt;T&gt; Find(Expression&lt;Func&lt;T, bool&gt;&gt; predicate); T First(Expression&lt;Func&lt;T, bool&gt;&gt; predicate); T FirstOrDefault(Expression&lt;Func&lt;T, bool&gt;&gt; predicate); T GetById(int id); void Add(T entity); void Delete(T entity); } </code></pre> <p>Here is the interface for the UnitOfWork (Note: Topic is a entity from my EF model):</p> <pre><code>public interface IUnitOfWork : IDisposable { IRepository&lt;Topic&gt; TopicRepository { get; } void Commit(); } </code></pre> <p>I am implementing the IRepository as such:</p> <pre><code>public class Repository&lt;T&gt; : IRepository&lt;T&gt; where T : class { private readonly DbSet&lt;T&gt; _db; public Repository(DbSet&lt;T&gt; db) { this._db = db; } public IQueryable&lt;T&gt; AsQueryable() { throw new NotImplementedException(); } public IEnumerable&lt;T&gt; GetAll() { return this._db; } ... etc } </code></pre> <p>This is the implementation of the UnitOfWork class:</p> <pre><code> public class UnitOfWork : DbContext, IUnitOfWork { private readonly Repository&lt;Topic&gt; _TopicRepository; public DbSet&lt;Topic&gt; Topics { get; set; } public UnitOfWork() { this._TopicRepository = new Repository&lt;Topic&gt;(Topics); } public IRepository&lt;Topic&gt; TopicRepository { get { return this._TopicRepository; } } public void Commit() { this.SaveChanges(); } } </code></pre> <p>I am calling:</p> <pre><code>this._unitOfWork.TopicRepository.GetAll(); </code></pre> <p>which returns zero topics when at least 2 exist in the database. The question I have is I am assuming this makes perfect sense as I no where defined or associated the DbSet to be associated to the CommonGoodEntities(class that was generated by adding the model) that the EF model generated, however how do I associate the two?</p> <p>I hope this makes sense. Essentially I want the UnitOfWork class to use my Entities class.<br> Am I going about this the wrong way?</p> <p>Thanks a lot in advance.</p> <p>Edit:</p> <p>I updated the Unit of work class based on SimonBelanger's comments. After doing so I was able to get it to work with the below code, however, I am not sure it is 100% correct. Is this what I should be doing?</p> <pre><code>public class UnitOfWork : IUnitOfWork { private readonly Repository&lt;Topic&gt; _TopicRepository; private CommonGoodEntities _db; public DbSet&lt;Topic&gt; Topics { get; set; } public UnitOfWork() { this._db = new CommonGoodEntities(); //this._TopicRepository = new Repository&lt;Topic&gt;(Topics); this._TopicRepository = new Repository&lt;Topic&gt;(this._db.Set&lt;Topic&gt;()); } ... etc } </code></pre>
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    1. COIf you are going to use the Unit of Work / Repository pattern, your `UnitOfWork` class should not directly inherit `DbContext`. You should, ideally, have a separate `DbContext`,instantiate it in the constructor and keep it in a private field (that can be Lazy too). Also, is this code first or DB first (with an EDMX file and generated `DbContext` and models) ?
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      1. POGeneric Repository - MVC 4 with Linq to Entities
      1. USSimon Belanger
    2. COWhat does `_unitOfWork.Topics.ToList();` return?
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      1. POGeneric Repository - MVC 4 with Linq to Entities
      1. USKeith Payne
    3. CO@SimonBelanger - thanks for clarifying that. I now removed the inheritance of DbContext and followed the advice you suggested by adding a private field to my CommonGoodEntities class and instantiating it in the constructor. Now that I have that, how would I modify my Repository class? This is using DB first utilizing an EDMX file and generated DbContext and models.
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